I was wondering if there are any special tricks to encourage the germination of rosa spinosissima & hybrids seeds (OPS) ? I have tried regular stratification techniques with a few, (Scotch Yellow, Hugnois, Kakwa, Scotch Pink, all OPS) so far with no success, unless they need a lengthier ( 2> months) cold stratification ?
Warm stratification before cold is what has improved germination of spins for me. Leave the seeds in moist medium at room temp for a couple months before cold and then after the cold treatment you have higher and more uniform germination. This has been the case for many of the North American species (R. arkansana, etc.) too. It is well documented in the Caninae section as well to help. Maybe Larry Davis has some suggestions with nitrate and smoke.
Thanks, I skipped the warm stratification, will do so.
I did the warm stratification on all of my seeds for the first time this year and I am eager to see if it helps. In the past I had little or no germination on R. nitida, for example. This is the first year I have R. arkansana seeds in the soil, too, so I’m glad I did the stratification.
I can’t speak directly to spins, but for R ark, nitrate treatment works OK. I’ve never gotten above 50 % with R. ark under any condition I’ve tried. We have chalcid infestation of hips around here. I can see some bad achenes, but can’t be bothered trying to find all of them and remove them before stratification. Generally for many kinds of hybrids nitrate outdoes warm stratification, and if used along with warm may give even higher germ, as with some caninas I discussed in a recent newsletter. However, the added N sometimes makes mold grow in the warm phase if you have some defective seeds to provide C. I’ve never found warm to be essential if nitrate is used in continuous cold.
This year I seem to have an exception to the nitrate rule with R beggeriana where karrikin (kar1) is really beneficial but nitrate is no better than just water. That was with early Aug. harvested seed put immediately to stratification within 3 days of hip harvest.
For many seeds, mediterranean conditions seem to be best, warm days, cool nights close to freezing. I did a quick test of this with a cool greenhouse, but Kim (roseseek) and some early students of germination in Italy and France observed this repeatedly.
I am going to try both methods, also with some OPS of Metis with no germination. Thanks for the advice.
A long-term experiment going now is using old seeds of R canina stored cold/dry for a couple years. There are reports of some kinds of seeds actually getting better at germ % over years of storage. So don’t give up on seeds if they fail the first time. Last spring I pitched out a bunch of vermiculite from the previous year’s studies and had over 100 sprouts as it sat in a pot in the garden. I think most were probably caninas
The testae of spin embryos tend to be dark and waxy which indicates lots of abcissic acid precursor. This makes sense given the geographic range for the spins - they need to survive long winters and short growing seasons relative to their tender cousins. I can’t speak directly to stratification strategies with respect to the spins but it would seem reasonable to play a long game.
On a related topic, I tried to find Jim Sproul’s (aka rosesbydesign) post outlining his stratification protocol which, if you can find it, would be good advice to follow especially for long stratification periods. IIRC he basically eliminated stratification media, does an adequate imbibing soak and towels dry prior to cold stratification - but do look for the post, I may have it partly incorrect.
Keep in mind it usually takes 18 - 24 months for Rosa spinosissima seeds to germinate.
An efficient way to germinate these seeds is the following method (seeds germinate uniformly and no transplanting of newly sprouted seedlings is necessary).
- Plant seeds in a container filled with soil.
- Provide two months warm treatment (room temperature), keeping the soil most.
- Place container in a fridge all winter and keep the soil moist.
- In the spring, put the container outdoors, keeping the soil moist.
- In early fall, bury the container in the garden or a flower bed.
- In late spring, dig up the container. Seeds should have germinated or will shortly afterwards.
I had no idea about the 18 to 24 months for spinosissima seeds, will definitely keep that in mind , in the past I have tried a variant of #1 to #4 for other seeds , instead of #3 , I have placed the container outdoors by mid February and let it be and waited for germination outdoors in May , that has worked with good results, I will try the full wait cycle. Thanks
If you don’t want to wait 18 to 24 months for your spin seeds to germinate, Don has had success extracting embryos from spin seeds. Back in 2009 he sent me embryos of OP seeds from Harrison Yellow, Prairie Peace and Ross Rambler #1. I tried extracting embryos of seeds from a couple of these plants but I didn’t have any success. But that may been because I didn’t follow the proper procedure since none of the embryos I extracted grew. But if you have extra seed that you are willing to try extracting the embryos from, it may be worth your while.
I like the "and hybrid’ part. The seeds are so much easier that are straight Scot. So get the pollen from the scot and pollinate away. Even my F2s get away from the difficulties of germination. I have done extraction of prairie peace because it was slow I only got one good seedling.
This would be slightly going off topic but in an old French Rose book, available as a full free scan by Google "Le Rosier, Lachaume 1874 , pages 32 to 34 describes how they used to grow rose seeds back in the day, outdoors, to start with they would do so starting in October and into mid December, depending on the climate, one method “semis en plein terre” is planting the seeds outdoors directly in garden soil and covering them with a slight layer of sand and then leaves, another one “semis sous cloche” is planting the seeds directly in the ground covering them with a pot like “botanic bell ?” surrounded by compost and dried leaves , and so on… all of them leaving the seeds to the elements and temperature fluctuations for the duration of winter and uncovering them in spring with a few spot checks in between,with the wild life in my area trying this would be rather challenging, but I will translate this 3 4 pages and post them when I get a chance.
I like the "and hybrid’ part. The seeds are so much easier that are straight Scot. So get the pollen from the scot and pollinate away. Even my F2s get away from the difficulties of germination. I have done extraction of prairie peace because it was slow I only got one good seedling.
I agree Johannes I was going to suggest the same thing. I’ve had better luck using the Scot as the pollen parent also (but not much better though).
I assumed Hovman had some Scots seeds he wanted to germinate and that’s why I suggested the embryo extraction.
My scot seeds are OPS , not the result of conscious pollination , the reason I included hybrid in the subject line is some consider kakwa to be a hybrid although there is some dispute if it is a true hybrid or not, I can try some pollination using them this spring, what would a cross of laxa x spin look like ? Or what would be the chances of its success ?
‘Kakwa’ is likely a selfed Rosa spinosissima (Double Scotch). It wasn’t distinctive enough in appearance to warrant introduction.
“…what would a cross of laxa x spin look like?”
Have a look at photos of ‘Haidee’ and ‘Suzanne’ on HMF Roses and there is your answer, when the likely Spinosissima used was ‘Stanwell Perpetual’.
I would have liked to have seen much more work done in this respect over the years, particularly using yellow Spinosissimas as the staminate parent. But even Rosa laxa x Rosa spinosissima (Double Scotch) or 'Kakwa would be interesting to me. Selections could be used for further breeding.
Chances of success of Rosa laxa x R. spinosissima are likely fair to good. It seems sometimes Rosa laxa can be reluctant to accept foreign pollen, but it certainly has been done.
Has anyone used heat to disable the inhibitors on the stigma? I have heard about the genus Dortis requiring it when making wide crosses-at leased as I remember. One Prof did the crosses and I did the extraction of the “seed” and did the culturing on Agar.
I have also cut pistols of Lillium so the pollen does not have to travel as far.
It would be interesting to see if these would work.